1. Field of the Invention
The present invention relates to a load damping system, applicable to sliding block adapters used for the transmission of motion generated by a motor connected thereto. Such a system finds application, for example, in the transmission of motion from the motors to the rolls of a rolling stand for flat products. In particular, the present invention relates to an elastic junction for the dynamic connection between the motor side and the adapter head, or between adapter and rolling rolls, such as to ensure the reduction of the axial tensions that are transmitted along the adapter in response to stresses generated during rolling.
2. Background Art
Two types of sliding block adapters are known in the art: fixed adapters and telescopic adapters. The first ones form a rigid body, while the latter have the possibility to vary the axial extension thereof. In the exemplary case of a rolling plant, this second solution allows shifting the rolls or rolling cylinders. Disadvantageously, both types of adapters, and in particular fixed adapters, transmit the axial component of the load, that is generated during the rolling, to the motor. The rolling stand, for example, can in fact generate axial loads due to various phenomena related to the rolling process, which through the adapters can be transmitted from the rolling cylinders to the motor. The ends of the working rolls of the stand, on the side opposite that of the adapters, are accommodated in a chock. Between the chock and the relative fixed shoulder there is a predetermined clearance which, by design, normally has a nominal value of about 1 mm, while it can actually also reach 3-4 mm, being the result of a sum of tolerances and also due to possible wear that may occur over time.
The thrust bearings of the motors generally have an axial clearance limited to ±0.35 mm for reasons of intrinsic functioning of the motors which, therefore, can be still affected by the axial loads generated by the rolling stand since the axial clearance between chocks and shoulders is greater than that of the thrust bearing of the motor.
Thus, the axial forces which develop during the rolling make such a clearance closed, and such forces are then transmitted to the motors through the adapters. These loads are harmful to the motors, which precisely to oppose such stresses are normally provided with radial or axial thrust bearings suitably sized according to the maximum load, since any failure of said bearings would entail putting the motor out of order.
In plants having this size and these features, such as rolling plants, the main motors are absolutely vital for production, and it is therefore essential to prevent failure of these members, which could lead to a shutdown of months also due to the fact that often spare parts are not available in a short time for components of this type and size (these are motors whose power can reach up to 10,000 kW). A plant shutdown is obviously the most negative factor which a producer can experience, as it involves a loss of productivity. Therefore, in order to prevent this from occurring, it is preferred to oversize the axial bearing of the motor, even if this implies a substantial increase in the size of the total expenditure: both radial and axial motor bearings are very expensive and their size consistently impacts the total cost of motors. In the prior art, the junctions between the sliding block adapters and the flanges on the roll side or on the motor side essentially consist of axially rigid systems that, due to such a rigidity, transmit all the loads from the rolling stand to the motor. That is, the adapter junctions are generally obtained by rigidly constraining the constituting parts.
A first example of this type of system is provided by document U.S. Pat. No. 7,582,019B2 in which two sections of an adapter are interconnected through a system of compensation of the axial loads which provides for the use of longitudinal cylindrical dampers arranged both within the connection itself and outside of it. The inner cylinders consist of a guiding jacket within which a sliding damper element can move, whose rectilinear motion takes place along the longitudinal axis of the adapter. This frictional non-rotatable connection is coupled to the outer cylindrical dampers which absorb the axial forces and prevent the twisting of the two interconnected segments of the adapter. In this way, however, this double connection has a rigidity that prevents the effective absorption of the transverse and torsion stresses that normally affect the normal operation of the adapters. This gives the system a lack of elasticity precisely where the greatest stresses coming from the rolling system are formed.
A second axially rigid interconnection system is described in document U.S. Pat. No. 7,784,380. The system involves the use of an interconnection between a flange and the head of an adapter consisting of a housing block rigidly fixed to the end of the adapter and within which a pressure bar is longitudinally arranged. The orientation and the shape of the bar are aimed to withstand and balance the axial thrust and traction loads, while its angular movement is limited by the design degree of freedom of the housing block. Also this solution is therefore affected by the transverse rigidity and torsion rigidity which do not allow the elastic absorption of all the tensions and stresses to which the adapter head is subjected.
In both cases described above, as in every other solution currently adopted in the prior art, a component which is essential for the effective reduction of the loads transmitted to the adapter is therefore lacking, i.e. the elastic and pluridirectional response to such loads, which may effectively reduce any risk for the integrity of the connection junctions and, in particular, of the motors.